An important element of cranes is the crane tower, which accounts to a substantial degree for the achievable crane hook height. In top-slewing tower cranes, the crane tower has the function of dissipating the occurring loads from the upper part of the crane as well as forces acting on the upper part to the base point of the crane tower.
Forces occurring and straining the crane tower are in particular the dead weight of the crane components, loads occurring due to momentums caused by a load on a load hook or by a counter ballast on the counter jib, loads resulting from traveling movements of the crane and loads caused when the crane is subjected to wind.
In conventional cranes, the various influences and loads are typically dissipated by selecting a suitable structural design of the tower. In most cases, the tower is therefore configured as a truss supporting structure, in the case of which the bending moments occurring, i.e. moments that may result in a deformation of the crane tower which projects perpendicularly from the base, are dissipated via usually three or four corner posts. The horizontal moments and the torsional loads are dissipated to the base point via the bracing with diagonal elements in the crane tower.
The dimensions of welded components are here normally chosen such that the maximum admissible dimensional limits for transport will not be exceeded and that the transport can still be carried out at a reasonable price.
Aspects that are opposed to this endeavor are the highest possible hook height and the highest possible bending resistance of the crane, which necessitate suitable dimensions of the components of the tower, whereby the crane tower is rendered heavy and expensive. These two opposite endeavors cannot be united by conventional cranes. The maximum hook height remains limited, since certain limits are set by the economy of transport and also by the realization of a crane transport. If particularly high hook heights are required, the cross-section of the tower is therefore stepped, with larger tower components being used in a lower area of the crane tower. Towards the upper end, the tower cross-section gets smaller step by step. Nevertheless, the transport expenditure is enormous.
It is the object of the present invention to increase the load bearing capacity of a crane tower and to dimension the components of a crane tower such that they can be transported more easily and have smaller transport dimensions, although their load capacity remains the same.
This object is achieved by a crane tower having a crane tower base, which has a crane tower fixed thereto and from which the crane tower extends upwards, and a tension element for bracing the crane tower on the crane tower base, the tension element having one of two ends connected to the crane tower base and the respective other end connected to the crane tower or to a coupling element that is connected to the crane tower, wherein the tension element extends outside of the crane tower.
The crane tower comprises here a crane tower base, which has a crane tower fixed thereto and from which the crane tower extends upwards, and a tension element for bracing the crane tower on the crane tower base, the tension element having one of its two ends connected to the crane tower base and its respective other end connected to the crane tower or to a coupling element that is connected to the crane tower. In addition, the crane tower is characterized in that the tension element extends outside of the crane tower.
A crane tower is a crane superstructure which stands up preferably vertically and which has the crane jib fixed thereto and thus accounts to a substantial degree for the achievable crane hook height. Typically, the crane tower consists of a plurality of interconnectable mast sections representing individual elements of the crane tower that are adapted to be connected to one another. In the case of “climbing-type” cranes, mast sections are incorporated into a crane tower which is already connected to the fully assembled upper part of the crane. This is normally done by means of a hydraulic pump arranged on the crane tower, said hydraulic pump pressing the upper part of the crane upwards thus providing free space for a mast section element to be inserted. By repeating the insertion process, the crane tower increases in height. The term mast section stands for prefabricated subsections of the crane tower.
The crane tower base describes the element from which the crane tower extends upwards and which transmits the forces coming from the crane tower into the ground. The crane tower base may e.g. be a crane foundation, an X-pattern foundation or an undercarriage. The crane foundation is normally a concrete foundation whose upper side is preferably approximately flush with the ground level.
The tension element for bracing the crane tower preferably comprises a brace and/or a rope. By means of the tension element, a point of the crane tower or a coupling element connected to the crane tower is connected to the crane tower base via the tension element, so that the point of the crane tower connected to the tension element, or the coupling element is pulled in the direction of the crane tower base or braced.
In addition, the tension element extends outside of the crane tower. Preferably, this means that the cross-sectional area defined by the plurality of corner posts of the mast section and of the crane tower, respectively, will not collide with a tension element.
A coupling element that may perhaps also be rigidly connected to the crane tower is not taken into account in the definition of the cross-sectional area of the crane tower, since a coupling element does not have any influence whatsoever on the maximum dissipatable bending forces of a crane tower. Hence, the only important aspect preferably is that the tension element extends outside of a cross-sectional area of the crane tower, whose corner points are defined by the plurality of corner posts of the crane tower, preferably by three or four such corner posts.
A coupling element may be considered to be any element which projects rigidly from the crane tower and which comprises a point outside of the cross-sectional area defined by the plurality of corner posts of a crane. A typical characteristic of a coupling element is that it is rigidly connected to the crane tower and that it has a fundamentally rigid basic structure. Preferably, the coupling element of a crane tower may be a bracket, an adapter piece to a different type of crane tower or a ball slewing ring support. As has already been explained hereinbefore, it will be of advantage when the point connected to the tension element is located outside of a cross-sectional area of a crane tower element (mast section). The cross-section extends in a plane which is perpendicular to the longitudinal direction of the crane tower. The cross-sectional area is preferably determined by the mast section that is directly connected to the crane tower base.
It follows that, when the crane element connected to the crane tower base has a cross-sectional area which is smaller than that of a mast section arranged above said crane element, a connection of the tension element at points located beyond the cross-sectional area of the mast section connected to the crane tower base is comprised by the present invention.
Preferably, the coupling element, which is connected to one end of the tension element, projects from the crane tower. It projects advantageously in a direction perpendicular to the longitudinal direction of the crane tower.
According to a further, optional, advantageous feature, the tension element extends substantially parallel to the longitudinal direction of the crane tower, i.e. in the case of a rotating tower crane it extends substantially parallel to the vertical. This arrangement of the tension element leads to a space-saving realization of the invention, since a compact crane tower base will here accompany the realization of the invention. Moreover, when a tension element extends parallel to the longitudinal direction of the crane tower, the amount of material that has to be used for the tension element with regard to a maximum height to be reached will be minimal.
Preferably, the crane tower according to the present invention comprises a second tension element, said second tension element being preferably arranged such that it is located in a common plane together with the first tension element, said plane comprising the longitudinal direction of the crane tower or extending parallel to the longitudinal direction of the crane tower. By providing a second tension element, the bending moments acting on the crane can be compensated for in more than one direction. The person skilled in the art will be aware that the present invention is not limited to a maximum of two tension elements. On the contrary, it makes sense to provide additional tension elements so as to compensate or weaken bending forces occurring from several directions with the aid of a plurality of tension elements.
An additional advantageous further development of the invention describes that the first tension element and the second tension element are arranged mirror-symmetrically with respect to a mirror plane, the mirror plane extending preferably through the longitudinal axis of the crane tower. In this context, each of the first and second tension elements may also be connected to an associated coupling element (provided separately for each of the tension elements). Preferably, it is also possible that both tension elements extend parallel to the longitudinal axis of the crane tower.
In this context, it is imaginable to configure the tension element as a jacketed, high-strength fiber rope, the fiber rope comprising preferably aramid fibers. These high-strength, jacketed fiber ropes are able to bear particularly high loads and are particularly resistant and their load bearing capacity can easily be adapted to the characteristics demanded. Moreover, they have a very low weight and, due to their flexibility, they are ideal for forming tension members of increased length. In addition, they can be transported preferably in a condition in which they are wound onto a drum and they can be installed with little mounting effort. This results in savings as regards crane transport and mounting.
Preferably, it is also imaginable to provide a structural design of a crane tower comprising a plurality of coupling elements, which project from the crane tower and are arranged one above the other in a vertical direction and in the case of which the tension element extends from a next higher coupling element to a coupling element located therebelow, and is connected to the latter.
The crane tower base is here the section of the crane tower, which is connected to the coupling element located below a next higher coupling element. A crane tower element, which preferably corresponds to a mast section, extends from the crane tower base upwards and is connected to the crane tower base via a tension element. Hence, a plurality of bracing planes is formed, and planes adjoining one another are interconnected by a tension element. This realization of the invention is particularly advisable in the case of climbing-type cranes. Thus, a crane tower according to the present invention will be realizable, i.e. the crane tower can be provided with a tension element, when a specific height has been reached, and also the tension elements can be allowed to climb as the height of the crane increases.
The present invention additionally relates to a rotating tower crane including a crane tower according to one of the preceding embodiments, the rotating tower crane being preferably a top-slewing tower crane.
Additional advantages and details will be described in more detail hereinafter making reference to the embodiments shown in the drawings.